FINAL INSPECTIONOMPLEMENTATION REPORT

FOR THE

OFE-POST MAGE TASK

ROCKY MOUNTAIN ARSENAL

AUGUST 1997

INTRODUM0

The Rocky Mountain Arsenal (RMA) was established in 1942 to manufacture chemical warfare

agents and incendiary munitions for use in World War IL Following the war and through the

early 1980's, the facilities continued to be used by the Army. Beginning in 1946, some facilities

were leased to private companies to manufacture industrial and agricultural chemicals. Shell Oil

Company, the principal lessee, primarily manufactured pesticides from 1952 to 1982. Common

industrial and waste disposal practices used during these years resulted in contamination of

structures, soil, surface water, sediment and groundwater.

The RMA Superfund Site is comprised of two areal units, On Post and Off Post. The On post

unit is encompassed by the boundaries of RMA; occupying 27 square miles in southern Adams

County, approximately 8 miles northeast of Denver. The Off Post unit is located immediately

north of RMA as shown in Figure 1.

The Record of Decision for the Off-post Operable Unit (12/19/96) for Rocky Mountain Arsenal

specified that approximately 160 acres in the southeast portion of Section 14 and the southwest

portion of Section 13 (Figure 2) would be tilled and seeded with an appropriate seed mix. The

objective of this project was to thoroughly n-Ax the top 8-10 inches of soil through tillage of

appropriate areas within the area of estimated dieldrin concentration greater than 0.04 ug/g, and

establish self sustaining vegetation at those sites.

This project was conducted as a cooperative effort among the Army, Shell and the U.S. Fish and

Wildlife Service (the Service). The Army provided fuel for the project. Shell provided project

oversight, administrative responsibilities, some equipment, seed and partial labor. The Service

provided a large horsepower tractor for pulling the Rotoclear, seed broadcasting equipment and

tractor operators.

Operator training began on March 1, 1996 and the project work was completed on April 16,

1996. Only minor delays due to inclement weather and equipment maintenance and repair

occurred during the project.

DESCRIPTION OF BEYEGETATION ACTIVITES

The magnitude of this project was limited to soil tillage and seeding as detailed in a Task Plan

finalized on March 18, 1996. The Task Plan incorporated goals (see Appendix B) by which the

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success of the tilling and revegetation could be measured. The soil was tilled and thoroughly

mixed to a depth of 8-10 inches by a Madge Rotoclear implement pulled by a large horsepower

agricultural tractor. Observation of the equipment during operation and visual inspection of the

tilled areas by representatives of all Parties resulted in agreement that only one pass was needed

for thorough mixing. After tilling, seed was broadcast over the soil surface and incorporated into

the soil through light harrowing to ensure good soil/seed contact.

Two different seed mixes were planted. A diverse native mix (Table 1) consisting of species

adapted to the local climate was used for areas around the reservoir and adjacent to the wetland

areas bordering First Creek (Figure 2). This site had been over grazed and the vegetation

community quite degraded. Species. selected for the native seed mix were included to

complement residual vegetation (e.g. inland saltgrass, Wia&Wia stricta) and sand dropseed

Sporobolus rvotandius) that would likely volunteer at the site from existing plant material.

Because of their proximity to First Creek, these areas will likely not be disturbed in the future.

The objective for the areas adjacent to the creek, therefore, was to restore ecologically diverse

wildlife habitat. Upland sites were treated differently since future land use as wildlife habitat is

less certain. These areas were seeded with a mix consisting of crested wheatgrass, alfalfa and

fourwing saltbush (Table 2). This mix, although less diverse, consists of species easily established

that will stabilize soils for the long term while providing some habitat suitability during the open

space nature of the site.

Table 1. Seed Mix for Tilled Areas Adjacent to First Creek

Lbs. PLS/

Scientific Name Common Nam Variet Acre*

Pasco=on smitWi Western Wheatgrass Arriba 7.6

Panicurn virgatum Switchgrass Nebraska 28 1.2

Elyms canadensis Canada Wildrye Native 3.5

Gaillardia aristata Blanket Flower Native 0.1

Unum lewisfi Blue Flax Native 0.1

Helianthus amms Annual Sunflower Native 0.1

Achillea lanulo Yarrow Native 0.01

Ratibida columnifera Prairie Coneflower Native 0.1

DiLp-a puipu Purple Prairie Clover Native

Total 12.81

*Lbs. PLS/Acre = pounds of pure live seed per acre

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Table 2. Seed Mix for Upland Tilled Areas

Lbs. PLS/

Scientific Name Common Name Vangty Acre*

Aero=on cristatum Crested Wheatgrass Hycrest 9.0

Atriplex canescens Fourwing Saltbush Native 0.2

Medicaizo afim Alfalfa Ladac 1.5

Total - 10.7

*Lbs. PLS/Acre = pounds of pure live seed per acre

STATUS QE REVEGETATION

Visual inspection of the site was conducted monthly after seeding was completed on April 16,

1996. Although different seed mixes were used in the two potential future land use zones, each

zone responded similarly. In October, 1996 vegetation dominating the entire site consisted of

plants that volunteered from existing plant material that survived the tilling process or plants that

grew from seed that existed in the soil seed bank. Seedlings of seeded species were not as

noticeable, although these could be found with attentive inspection. Crested wheatgrass, alfalfa

and weedy perennial and annual forb species occurred in the upland site, while inland saltgrass and

weedy perennial and annual forbs re-established in the lower areas.

Based upon experience gained through revegetation efforts over the past eight years in the Onpost Operable Unit, results observed in the Off Post area were not unexpected. Dramatic

establishment and growth of seeded species usually does not occur during the first growing

season. In this case, two factors were primarily responsible for the observed result. First,

existing, more mature plant material has a competitive advantage over seedlings and usually

dominate revegetation efforts when present. Secondly, climatic conditions occurring in the

months following seeding were not conducive to extensive seedling growth. Precipitation was

low for nearly all months of the growing season (Table 3). The month of May had average

precipitation, but the moisture mainly came at the end of the month when temperatures were high

so that effective precipitation was low. The distribution of precipitation post seeding certainly

promoted establishment and growth of the weedy warm season species kochia. Because of the

height and density of this species, most of the site was mowed mid-summer to prevent shading of

desirable seedlings.

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Table 3. Inches of precipitation/percent of long term average (1948-1995) recorded at the

National Weather Service Denver field office for months following seeding of the off-post

area in 1996.

April May* June July August September

NWS** 0.48 2.73 1.58 1.22 0.26 NA

(27%) (108%) (93%) (66%) (18%)

0.31 2.29 1.13 0.86 0.42 2.46

(18%) (91% (67%) (47%) (420/-) (218%)

Note that more than 80% of this months total came during the last 8 days of the month.

**Data from the National Weather Service Denver field office

***Data from a monitoring station at the Shell Trenches site at Rocky Mountain Arsenal.

One problematic effect of the tillage program is that Canada thistle, a noxious weed species,

became widely re-established over the site. Since Shell acquired the property in 1991,

considerable effort has been expended to control established populations of this troublesome

plant species. Significant effort will again be required to prevent Canada thistle populations on

Shell property from becoming a nuisance to adjoining agricultural and housing development land.

Goals stated in the task plan for this project were for establishment of a minimum average of one

perennial grassland species per square meter with no visible soil erosion within the tilled area.

Both visual inspection and quantitative estimates of perennial plant density and annual plant cover

(Table 4) indicate that goals have been met. There is no evidence of soil erosion, i.e. there are no

rills indicating erosion by water or wind deposited/eroded soils. Although the plant community is

still developing, there is sufficient plant cover to prevent any erosion developing over winter.

Confirmation of these observations was made by representatives of the Parties during the final

inspection of the site which occurred on October 17, 1996.

Two types of vegetation data were collected to verify visual observations. Individual plants were

counted in randomly placed 1-square meter quadrats to estimate perennial plant density for the

site, and insure that the goal of one perennial plant per square meter was met. In addition, total

cover by annual species was estimated as further indication of soil stabilization. Cover by annual

species was the selected metric because it was not practical to count the numerous annual

individuals.

Average perennial plant density for the native seeded area was approximately 29 and 10 for the

upland seeded area (Table 4). These values are well above the goal set for the project. In

addition, mean cover by annual species was 29 percent for both the native area and the upland

locations (Table 4). In combination, these values indicate that vegetation is well established in

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tilled areas of the Off:-post Operable Unit.

Table 4. Summary Statistics for Perennial Plant Density and Annual Plant Cover

Estimates Based on Data from Randomly Placed I -square meter Quadrats.

Native Seeded AM Upland Seeded Am

Number of quadrats 38 72

Mean number of perennial plants 29.4 9.8

Standard Deviation 36.2 12.1

Range 0-127 0-87

Mean percent annual plant cover 28.9 28.8

Standard Deviation 14.9 21.8

Range 5-60 5-90

RECOMNHIbMATIONS FDR MAINTENANCE ACTFVI M-S

Maintenance of the tilled area will be conducted by Shell, owners of the property. Maintenance

activities will include but not be limited to: control of noxious plant species and other weedy plant

species that may interfere with establishment of self-sustaining vegetation and re-seeding areas

that failed to establish.

Specific maintenance operations that will be conducted during the fall of 1996 and during 1997

include control actions targeting Canada thistle populations and mowing annual weedy species,

especially kochia, to promote establishing desirable species. Overseeding areas with little

establishment of perennial grasses may be suggested for fall 1997 if an additional growing season

does not produce suitable results.

LESSONS LEARNED

1. Established perennial vegetation, especially crested wheatgrass, inland saltgrass and field

bindweed, has a high probability of re-establishing after a single tillage regardless of how

thoroughly the soil is tilled at that time. Many habitat improvement projects to be conducted On

Post at RMA have the goal of changing crested wheatgrass stands into more diverse habitats. It

will be necessary to conduct additional control beyond a single tillage to eliminate established

plants prior to seeding with a diverse native seed mix.

2. The Madge Rotoclear thoroughly mixed soils after one pass of the implement, and its massive

power allowed tilling without any pre-clearing of existing vegetation. However, the intensive

maintenance that the implement requires, the large quantity of fuel consumed, and the limited

depth to which soils can be tilled may indicate that use of a deep plowing agricultural disc may be

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more efficient for most uses at RMA. The rotoclear would be most useful in areas such as

shrublands where considerable clearing of vegetation would be necessary before working soil.

PROJECT COSTS

The total cost estimated for the combined efforts of this project was $60,000. This amount

includes labor estimates, equipment rental, material cost and contingency. Actual cost of the

project was less as indicated below.

Labor: $18,247

Equipment: 17,794

Small tools/consurnables (Fuel): 1,415

Materials: 7,008

Fees/Distributable: §J31

Total 51,001

PROJECT SUMMARY

Following the pre-final inspection held at the Off Post unit on April 26, 1996, only growth of the

seeded areas had not occurred. All other activities, as mandated by the ROD and detailed in the

Task Plan, had been completed. By the time of the final inspection on October 17, 1996,

adequate growth of the seeded areas had occurred as documented in this report. This phase of

the Off Post remedy was a comprehensive "one-time correction" and does not require active

operation and/or maintenance other than routine vegetation maintenance to ensure compatibility

with surrounding land use. No modification of the activities delineated in the Task Plan was

required to complete this project. There are no outstanding construction items remaining from

the pre-final inspection.

CERTMCATTON

I hereby certify that the construction activities as identified in this document were performed in

accordance with the Off Post Record of Decision and the "Task Plan for Tilling and Revegetation

of 160 Acres of the Off Post Area."

-'Mr. Charles T. Scharmann

Remedy Execution Manager

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CHRONOLOGY 01 EYENTS

December 19, 1995 Record of Decision signed

February 14, 1996 Meeting of all Parties to review Task plan

February 20, 1996 Draft Task Plan mailed to all Parties

March 4, 1996 Operator training

March 11, 1996 Site visit by all Parties

March 18, 1996 Revised Final Task Plan mailed to all Parties

Tilling initiated

Public notice of availability of Task Plan for review

March 29, 1996 Mid-point site visit by all Parties

April 4, 1996 Public meeting for review/update of project

April 15, 1996 Tilling completed

April 16, 1996 Seeding completed

April 18, 1996 Draft Pre-final Inspection Report sent to all Parties

April 26, 1996 Pre-final inspection conducted

October, 1996 Draft Final Inspection Report

October 17, 1996 Final Inspection conducted

January 17, 1997 Draft Final Task/Implementation Report

June 6, 1997 Final Inspection/implementation construction report

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Appendix A: Pre-final Inspection Report

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PRE-FINAL IINSPECTTON REPORT

EM-ODUCTION

The Record of Decision for the Off-post Operable Unit (12/19/96) for Rocky Mountain Arsenal

specified that approximately 160 acres in the southeast portion of Section 14 and the southwest

portion of Section 13 would be tilled and seeded. The objective of this project was to thoroughly

mix the top 8-10 inches of soil through tillage of appropriate areas within the area of estimated

dieldrin concentration greater than 0.04 ug/g, and establish -self sustaining vegetation at those

sites. Tilling was conducted using a rotoclear which is a large rototiller type implement. An

appropriate seed mix was broadcast over tilled areas and harrowed to insure good soil/seed

contact.

This project was conducted as a cooperative effort among the Army, Shell and the U.S. Fish and

Wildlife Service (the Service). The Army provided fuel for the project. Shell provided project

oversight, administrative responsibilities, some equipment, seed and partial labor. The Service

provided a large horsepower tractor for pulling the rotoclear, seed broadcasting equipment and

tractor operators.

The project was initiated with operator training on March 1, 1996 and was completed on April

16, 1996. The work period included minor delays due to inclement weather and equipment

maintenance and repair. The tilled areas will be visually monitored to detect any large areas (i.e.,

areas greater than 0.01 acres) where revegetation has failed. Areas of this size that fail to

revegetate will be re-seeded in September, 1996.

DESCRIPTION DE AGRICULTURAL ACTBn=S

Activity for this project was limited to soil tillage and seeding. The soil was tilled and thoroughly

mixed to a depth of 8-10 inches by a rotoclear implement pulled by a large horsepower

agricultural tractor. Only one pass was needed for thorough mixing. After tilling, seed was

broadcast over the soil surface and incorporated into the soil through light harrowing. Two seed

mixes were used for this project. A diverse native mix consisting of species suitable for lower

topographic positions with higher soil moisture was used for areas around the reservoir and

adjacent to First Creek. These areas will likely not be disturbed in the future. Upland sites where

future land use is unknown were seeded with a mix consisting of crested wheatgrass, alfalfa and

fourwing saltbush. This mix will stabilize soils for the long term while providing adequate habitat

diversity during the open space use of the site.

DISCUSSION DE MAINTENANCE REQUrREMENTS

Maintenance of the tilled area will be conducted by Shell, owners of the property. Maintenance

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activities will include but not be limited to: control of noxious plant species and other weedy plant

species that may interfere with establishment of self-sustaining vegetation and re-seeding areas

that fail to establish.

FINAL INSPECTION DOCUMENTATION

A pre-final inspection will be scheduled for the week of April 22, 1996 and final inspection will

occur in September, 1996 after vegetation has been established and/or failed areas have been reseeded.

SUMMARY Of PROJEC COSTS

A summary of project costs will be provided with the Final Task Report due in November, 1996.

CHRONOLOGY DE EVENTS

December 19, 1995 Record of Decision signed

February 14, 1996 Meeting of all Parties to review Task plan

February 20, 1996 Draft Task Plan mailed to all Parties

March 4, 1996 Operator training

March 11, 1996 Site visit by all Parties

March 18, 1996 Revised Final Task Plan mailed to all Parties

Tilling initiated

Public notice of availability of Task Plan for review

March 29, 1996 Mid-point site visit by all Parties

April 4, 1996 Public meeting for review/update of project

April 15, 1996 Tilling completed

April 16, 1996 Seeding completed

April 18, 1996 Draft Pre-final Inspection Report sent to all Parties

April 26, 1996 Tentative date for pre-final inspection

August, 1996 Draft Final Inspection Report

September, 1996 Final Inspection

November, 1996 Final Task Report

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Appendix B: Task Plan for Tilling and Revegetation of 160 Acres of the Off-Post Area
TASK PLAN FOR TILLING AND REVEGETATION

OF 160 ACRES OF THE OFF-POST AREA

Task Description

The Agreement for a Conceptual Remedy for the Cleanup of the Rocky Mountain Arsenal and the

Record of Decision for the Off-post Operable Unit (12/19/95) specified that approximately 160

acres in the southeast portion of Section 14 and the southwest portion of Section 13 would be

tilled and seeded. Although a total of 160 acres will be tilled during this project, the tilling will

not be contiguous because wetlands, tree groves and other areas will not be included, as described

in a letter to Jeff Edson, CDPIHE (attached). Soil in the project area will be tilled and thoroughly

mixed to a depth of about twelve inches. The area will then be seeded with a n-dx of appropriate

plant species to protect soil from erosion and establish a self-sustaining plant community.

Site Description

The site is located immediately north of Rocky Mountain Arsenal (Figure 1). The terrain is

generally flat with slopes no greater than 5%. Soils are loam, sandy loam or wet to moderately

wet alluvial material. Vegetation types include areas that have been seeded with exotic grassland

species, degraded sites with a variety of weedy and native grassland species, planted tree groves,

and wetland sites. In addition there is a groundwater treatment facility with treatment plant and

extraction and injection wells, and buildings from a previous home site (Figure 2).

Objective

The objective of this project is:

To thoroughly mix the top 8-10 inches of soil through tillage of appropriate areas

within the area of estimated dieldrin concentration greater than 0.04 ug/g, and establish self

sustaining vegetation at those sites (Figure 3).

Goals

1. At the end of the first growing season following tilling, on average, a minimum of one

perennial grassland species per square meter will be established.

2. Also at the end of the first growing season, there will be no visible soil erosion

anywhere within the tilled area.

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It is necessary for this project is to produce a self sustaining plant community established in a

timely manner after tilling. This plant community can be composed of plant species that are

expected to volunteer from plant materials already on site or species that are being seeded during

the project. Soils will be stabilized by live plants or by mulch incorporated into the soil. After the

first growing season, the established plant communities will develop an appearance similar to

comparable grasslands in the region. The rate of this development will be dependant upon

climate, but will be enhanced to the extent possible by maintenance activity such as weed control

and mowing.

Methods

Soil tilling and mixing will be conducted with a specialized "industrial" type machine called a

rotomill or rotoclear. The device was initially developed to remove the top of asphalt roads

before resurfacing. The technique was modified by the coal mining industry to prepare mountain

shrublands and forested areas for direct haul salvage of topsoil. The rotoclear is pulled by a large

horsepower tractor. A toothed drum rotating at a relatively high rate incorporates all standing

biomass into the soil at a depth of 12 inches. The result is a thoroughly mixed profile to the 12

inch depth. Grassland seed mixtures would then be broadcast seeded and incorporated into the

soil by harrowing the soil surface.

Responsibilities

Shell will provide project oversight, all materials required, a small tractor for conducting

broadcast seeding and harrowing, and an operator for seeding and harrowing operations. Shell

will also lease the rotomill for use during this project. Following completion and final inspection

of the project, Shell will assume responsibility for producing a task report that will contain an

introduction, chronology of events, discussion of progress toward meeting revegetation goal, final

inspection documentation, certification that the project was effective, maintenance

recommendations, and a summary of cost.

The Service (U. S. Fish and Wildlife Service will provide a large horsepower tractor for pulling

the rotomill and tractor operator for the duration of the project (10-14 days) and seed

broadcasting equipment.

The U. S. Army, EPA and State will participate in prefinal and final inspections of the site. An

initial inspection will be scheduled soon after tillage is initiated in order to obtain concurrence

with the method by all parties before a large amount of tillage has occurred. A final inspection

will be scheduled after all tilling and seeding has been conducted. Subsequent inspection may be

scheduled to monitor the progress of plant community development.

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Potential Impacts to Communities

No impacts are anticipated to nearby communities through conducting this project. The activity is

simply soil tilling followed by broadcast seeding of grassland plant species. It is not different from

concurrent farming activity on adjacent properties. Noise, traffic or dust levels will not increase

detectably. The only noise associated with this project is that produced by operation of a farm

tractor and the rotoclear tiller. These will not operate near residential areas. Only two or three

people are required for implementation of the project. No other traffic is associated. Dust

emissions are not anticipated to be a problem. Adequate soil moisture while the activity is being

conducted and incorporation of a considerable amount of existing standing vegetation into the

tilled area as mulch will prevent deflation of soil particles. -Thus dust emissions will be

minimized. In the unlikely event that excessive amounts of dust are produced, a dust suppressant

will be applied.

Community Relations/Notification

The importance of community relations activities to keep communities informed of site actions

has been recognized through a variety of notification and discussion. Officials in the government

of Commerce City and the Tri-county Health Department, as well as all adjacent land owners

have been notified of the pending tilling and revegetation activity. Although a specific task plan

was not complete at the time, the agreement to revegetate 160 acres of the offpost area was

briefly discussed at public meetings held in conjunction with the Conceptual Remedy and

Proposed Plan documents. The task plan is simply a presentation of standard tillage and

revegetation activities and does not differ significantly from the plan presented during those public

meetings. In addition, there has not been a request to hold a public meeting to specifically discuss

this minor component of the offpost Record of Decision; however, if a request is made, a public

meeting will be held. An additional effort to keep the public informed about this activity will

include publishing information about the project in the newsletter that the Army sends out to local

and interested citizens.

Health and Safety

Work will be performed under existing Project Health and Safety plans, as well as a project

specific plan (attached) which will address considerations unique to operation of the rotomill, and

contingency plans specific to this project. These plans will be provided by Shell. The owner of

the roton-dll (Monarch and Associates) will conduct a training session prior to operation of the

rotomill.

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Cost Estimate

Total cost estimated for the combined efforts of this project is $60,000. This figure includes

labor estimates, equipment rental and seed cost, equipment use cost and contingency.

Schedule

Preferred starting date: March 1, 1996 (or sooner if weather conditions and

logistics allow)

Preferred completion date: Start date plus 20 work days or sooner

Draft pre-final inspection report: Completion date plus I work day

Pre-final inspection: Completion date plus 5 work days or sooner

Draft final inspection report: 30 days prior to Final Inspection

Final inspection: September, 1996

Final Task Report 60 days following final inspection

15
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1997

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